Hitherto, in the field of flame-retardant coating processing on a vehicle seat material, such as automotive seat material and railcar seat material, there have been used resin compounds containing a halogen-based compound typified by decabromodiphenyl ether blended therein, or an antimony-based compound typified by antimony trioxide blended therein.
In recent years, in view of environmental concerns, it is demanded to use a flame retarder (i.e., flame-retardant agent) other than the halogen-based compounds or the antimony-based compound, and accordingly, there are used phosphorus-based flame retarders having no melting point, typified by ammonium polyphosphate (APP), metal hydroxides such as aluminum hydroxide and magnesium hydroxide, phosphoric acid esters, etc.
In the vehicle seat material, the flame retardancy thereof is an essential performance for saving the life of a passenger. Accordingly, the use of a flame retarder having a “better” flame retardancy is indispensable, but it is pointed out that the above-mentioned metal hydroxides and phosphoric acid esters exhibit a flame retardancy which is inferior to that of the APP. In addition, the use of an organic phosphorus-based flame retarder has a problem of increasing the cost.
On the other hand, APP incurs a low cost while exhibiting a good flame retardancy and therefore, APP is widely used. However, APP is soluble in water and brings about a problem that water spotting or slime may be caused due to the steam treatment at the time of vehicle seat processing, so as to reduce the workability thereof. Herein, the “water spotting” means a phenomenon that, when a seat having water or steam which has been attached thereto after treatment, is dried, the portion to which the water or steam has been attached may be spotted, form a circular stain or be powdered.
In order to solve such a problem, Japanese Unexamined Patent Publication (JP-A, KOKAI) No. 2006-028488 (Patent Document 1) discloses a coating composition for a vehicle interior material, comprising: a synthetic resin emulsion in an amount of 100 mass parts (i.e., parts by mass) in terms of solid content; and 1 to 300 mass parts of one kind or two or more kinds of a non-halogen-based flame retarder added thereto, wherein the non-halogen-based flame retarder has been obtained by coating the surfaces of non-halogen-based flame retarder particles containing phosphorus and nitrogen, with a functional group-containing organosilicon resin. In addition, JP-A No. 2006-063125 (Patent Document 2) discloses a process comprising: preparing a composition of a polyphosphate-based flame-retardant from a polyphosphoric acid compound and a silicone-based resin; and blending the composition with an elastomer resin; and applying the resultant blend to flame-retardant treatment of a fiber product.
However, it is technically difficult to completely coat APP. Accordingly, the solubility of APP in water may be reduced by the methods according to Patent documents 1 and 2, it has been difficult for these methods to reduce the solubility of APP in water at high temperature, particularly, in hot water at 80° C. or more.
As the method using no halogen-based compound, JP-A No. 2006-233152 (Patent Document 3) discloses a flame-retardant fabric, which has attained formaldehyde emission in an amount of 0.1 ppm or less, and comprises: a fabric and a back coating layer of a back coating agent disposed on the surface of one side of the fabric, wherein the back coating agent comprises an acrylic-type copolymer resin having no methylol group in the acrylic monomer thereof; ammonium polyphosphate, a phosphoric acid ester, and a thickener in a specific ratio.
However, in the method according to Patent Document 3, the problem of APP solubility in water has not been solved yet.
In order to make the water spotting unnoticeable, for example, a certain method is practiced such that the thickness of cloth (vehicle seat material) is increased, or the design or color tone is devised. However, in this case, the weight of the cloth may be inevitably increased, or a certain restriction may be imposed on the design or decorative property of the cloth. Accordingly, there is demanded a non-halogen-based flame-retardant coating agent for a vehicle seat, which does not require the measures as mentioned above, and realizes a reduction in weight of a cloth, and also realizes a wide range of design or decorative properties of the cloth, to thereby achieve both of an excellent flame retardancy and suppression of the occurrence of water spotting in the non-halogen-based flame-retardant coating agent for a vehicle seat.